QAQC References

QA vs QC vs INSPECTION 1) a) b) c) d)

Aim of Quality Assurance Improve Quality and reducing faults(salah) and wastage(pembaziran). Improve Quality and reduce costs. Improve Quality whilst keeping costs to an acceptable level. Improve system used to implement Quality Assurance is Quality System.

2) a)

Benefits(faedah) of adopting(menerima tanggungjawab) Quality Assurance Implemented and managed Quality System should ensure that the company focuses on market needs and requirements. Lead to a reduction of costs due to a reduced number of faults and wastage. Measure of performance which will anable any areas for improvement to be indentified.

b) c)

3) a)

b) c)

What is Quality Assurance Quality Assurance should be considered(menimbang) as management tool when used within as management tool when used within a organization (internal Quality Assurance). Quality Assurance provides the Objective evidence(bukti) needed to give maximum confidence(keyakinan) for Quality. All those planned or systematic actions necessary to provide adequate(cukup) confidence that a product or services will satisfy given requirement for Quality.

4) a)

Scope of Quality Assurance Encompass(merangkumi) all parts of organization an activity i.e : planning, design, production, inspection, maintenance, administration, and callabration with suppliers and purchasers,should also organization Quality System.

5) a) b)

Inspection vs Quality Assurance QA is not inspection Inspection is one of important elements within system of Quality Assurance i.e : planning, design, production and etc.

6) a)

Inspection vs Quality Control operational techniques and activities is to full fill for Quality i.e : manufacturing Quality Control is more explanatory(penjelasan).

QA vs QC vs INSPECTION 7) a)

b) c)

8) a)

Quality Control vs Quality Assurance Quality Control deals which the actual measurement of Quality performance, this performance compare(berbanding) against what is required and action is taken on the difference(perbezaan) QC is ask the question, action being performed correctly. Quality Control will rarely do anything to correct problems relateting to management documention training and motivation. Quality Assurance apply to all aread which have and affects on Quality, action being performed correctly. Quality Assurance Standards Bitish Standards (BS 4778 Part 1)

OBJECTIVE OF VISUAL WELDING INSPECTOR AND WELDING INSPECTION

1) a) b) c)

Main Responsibility Code Compliance Workmanship control Documentation control

2) Personal Attributes a) Honestly b) Integrity c) Knowledgeable d) Good communicator e) Physically fit 3) Duties Of Visual Welding Inspector And Welding Inspector a) Duties Before Welding b) Duties During Welding c) Duties After Welding d) If Any Repair 4) Basic a) Observe b) Record c) Compare 5) Welding Checklist a) Before Welding Ø Familiarization to the relevant code and specification Ø Check welding equipment and calibration certificates Ø Material identification (size, type and condition) Ø Consumables ( size, type, condition, storage and handling) Ø Review/withness WPS and PQR test and record Ø Joint preparation(check) Ø Welder qualification test( review/withness) Ø Welding process involved Ø Check pre-heating before welding( if required)

OBJECTIVE OF VISUAL WELDING INSPECTOR AND WELDING INSPECTION

b)

During Welding Ø Check weather condition Ø Check clearance for welding/welder Ø Check welder indentification for weld Ø Check consumables as per wps used Ø Check welding parameters as per wps used Ø Check distartion control Ø Check interpass cleaning Ø Check run out length Ø Check interpass temperature Ø Check usage of line up clamps Ø Maintain daily log book

c)

After Welding Ø Perform visual inspection Ø Weld and welder indentification ( check) Ø Post weld heat treatment (if required) Ø Non-destructive testing (withness) Ø Acceptance standards of NDT Ø Repairs (if any) Ø Dimensional check (as per drawing) Ø Document control (welding reports)

d)

In the event of repair Ø Authorization for repair Ø Removal and preparation for repair Ø Testing of repair (visual and NDT)

OBJECTIVE OF VISUAL WELDING INSPECTOR AND WELDING INSPECTION

6)

Duties and Responsibility of a welding inspector Basically, Duties and Responsibility of a welding inspector are divided into 3 main section where it's not more then duties and responsibiles before welding, during welding and after welding completion.

1) 2) 3) 4) 5)

6) 7)

8)

9)

Before welding, the welding inspector shall be collect and familiarization with all relevant document or information aid (membantu) to welding activities such as : Familiarization with applicable codes, standards or clent specifications. Approved and latest revision drawing (AFC). Approved welding procedure specification carried with procedure qualification record. To check, qualified welder with relevant valid certificates and expired date. Also check the joint preparation to make sure it is are being prepared as per needed by AFC drawing and as allowed by WPS or code, the joint preparation shall be clean an free from contamination (percemaran). Inspect the material size, type and condition, carried with mill or test certificates. Check the consumables size, type and condition for electrode check type of flux covering, i.e : basic, rutile, celloluse. Also check the treatment, storage and handling of the electrode. Check the temperature shoukd baked the electrode. Carried with batch certificate, when inspect. Check the condition of welding machine, also review all calibration certificate for measuring devices, i.e: welding machine, measuring tape, calipers, electrode baking oven, pwht machine, pressure gauge and etc. Check the preheat i.e: minimum and maximum interpass temperature and preheat use flame type. The heating rate must be uniform.

OBJECTIVE OF VISUAL WELDING INSPECTOR AND WELDING INSPECTION

5) 6)

During welding, the welding inspector should once again check : Consumables to confirm( pastikan), condition and storage. The inspector also should check electrode use as per wps. Check the weather conditions. He also shall check travel spped current characteristic such as ampare, voltage, in order to control heat input. Welding polarity is also one of the element where he should look into interpass cleaning and interpass temperature is to ensure that soundness of weld metal. Check the welder identification to ensure the welder qualified to weld welding position as per wps. He also should monitor the preheat temperature as per wps. In order to control destortion, welding sequence should be taken into consideration

7)

at the welding inspector. The inspector also shall maintain the daily log book.

1) 2) 3)

4)

1) 2) 3) 4)

1)

Right after welding the inspector may perform visual inspection immediately to detect all kind of surface defect and weld size Before visual inspection carried out, the welded joint must be cleanliness and free from oil or grease. The inspector must withness Non-Destructive Testing( NDT) activities. Inspector should monitor and withness pwht it the procee is required. All the relevant record and report document involve during fabrication must submit to higher authorities. Event of the repair : If the is any sign at detect are detected during his visual inspection and all repair process shall be done before NDT and Pwht process.

2)

Report to higher authorities reagarding the repair.

3)

Marking detect area for repair.

4) 5) 6) 7)

Liaise with higher authorities for weld repair procedure. Monitor repair work, as per weld repair procedure. Withness the NDT if required. Collate all the relevant record and report document for repair work and submit to higher authorities.

WELD TERMINOLOGY 1) a)

Welds To joint two material by the aplication of heat or pressure.

2) a)

Joints A configuration of members.

3) a) b) c) d) e) f)

Type of joints Edge Corner Lap Tee Cruciform Butt

4) a) b) c) d) e) f)

Type of weld Fillet Spot Butt Edge Plug Compound

5) a) b) c) d) e)

Type of joint preparation Gap Root face Angle of bevel Included angle Root radius d c

b a

e

WELD TERMINOLOGY 6) a) b) c) d) e) f) g) h)

Weld zone terms Root Fusion zone Weld metal Weld zone Heat affectect zone Weld junction Fusion penetration Parent metal

G

B

H

D C

H

E A

D

G

F F

A

7) a) b) c)

Shape of a fillet weld in cross section by 3 terms : Mitre fillet Convex fillet Concave fillet

8) a)

Type of joint design Single "v"- Butt Included angle 60 - 70

b)

B

C

Single Bevel - Butt Angle of bevel 40 45

2 - 3mm mmmm c)

Angle of bevel 30 - 35mm

Single "u" - Butt

d)

Single "J" - Butt Angle of bevel 15 - 20

Included angle 15 -20

Root radius 5mm 2 - 3mm * Single "V" or single bevel for plate (Less thickness plate) * Single "U" or single "J" for plate (Thicker thickness plate)

Land

E

WELD TERMINOLOGY e)

weld toes

3

weld toes

2

1 = Root of Penetration 2 = Hot pass 3 & 4 = Fill pass 5,6 & 7 = Capping

7

6

5

4

1

f)

A

B

E

D

A = weld width B = excess weld metal C = excess penetration D = root width E = thickness of parent metal

C

g) b d

a

c

*

To check throat thickness Design = 0.7 x material thickness ( 6mm) = 6mm x 0.7 (formula) = 4.2 + 0.5mm(formula) = 4.7 = 4.2mm (minimum) , 4.7mm (maximum)

A = Nominal design B = Actual throat thickness C = Horizontal leg length D = Vertical leg length

WELD TERMINOLOGY *

To check leg length Material thickness (6mm) so, leg length = 6mm (minimum) material thickness (6mm) = so, (+) 3mm = 9mm (maximum)

h)

A-B = Lack of sidewall fusion B-C = Lack of RootFusion OR Lack of RootPenetration.

A B C

9)

Welding Positions (ISO 6947) A

B C

E

D

Vertical up PF (3G)

A = Overhead (PE) (4G) B = Horizontal overhead (PD) C = Horizontal (PC) (ZG) D = Horizontal vertical (PB) E = Flat (PA) (1G) a)

vertical position(pipe fixed horizontal) = PF,PG = 5G

b)

inclined position fixed = H - L 045 = 6G

45

c)

inclined position rotated = L45/PA = 1 FR

45

Vertical down PG (3G)

WELDING PROCESS 1) a)

General Welding is the process of joining two or more pieces of material together by bringing the atoms of each piece into such close contact that an atomic bond takes place, i.e: the separate pieces fuse together to form one.

2) a)

Type Of Welding Smaw = shielded metal( menyelamatkan logam) Arch welding( lengkungan menyatukan) (AWS) Mma = manual metal Arch (BS)

b)

GTAW = gas tungsten Arch welding (AWS) TIG = tungsten inert - gas (BS)

c)

GMAW = gas metal Arc welding (AWS) MIG = metal inert-gas (BS) MAG = metal active- gas (BS)

d)

SAW

e)

FCAW = flux cored Arc welding

f)

PAW

= plasma Arc welding

g)

ESW

= electroslag welding

= submerged Arc welding

WELDING PROCESS 2a) 1 2 3 4 5 6 7 8

Manual Metal Arch & Shielded Metal Arc Welding Process Characteristics Process Diagram Equipment Diagram Variables Consumables Typical detects Advantages & Disadvantages Safety Process Characteristics mma is an arc welding process, uses an arc between a molten tip of convered electrode to the base metal (OR) mma is an arc welding process, uses an arc between an electrode with flux covering to the weld pool. manual welding process. mma, type of power source is constant curent or drooping arc characteristics.

1

a)

b) c)

Y 20 15 100 105

O.C.V. (open circuit voltage) I

:- MMA, TIG, SUB-ARC > 1000 Amps 2

Process Diagram Power supply 1 OR 3

Power source ( Constant Current)

Electrode welding cable

Return cable

Ground cable

Base metal Welding table

WELDING PROCESS 3

a) b) c) d) 4

Types of welding machine (Plant) Transformer Dc Rectifier Engine Driven Inverter Type of flux covering used

a)

Basic = E 7018 ≈ CO²

b) c)

Rutile = E 6013 ≈ CO² Cellulose = E 6010 ≈ H²

5

a) b) c) d) e) 6

a) b) c)

Functions of flux covering To provide shielding gas to the weld pool to avoid atmospheric contamination. To stabilise th arc Easy to strike the arc Improve the mechanical properties of weld metal Act as deoxidiser by addition of xlloying elements ( e.g : silicon) Types of polarity DC + = (Direct current reverse polarity) DC - = (Direct current staight polarity) AC = (Alternative current)

DC +

DC -

* Shallow Penetration

WELDING PROCESS 7

a) b) c) d) e) f) 8

Variables Current Voltage Travel Speed Electrode andle Open circuit voltage ( O.C.V) Polarity Consumables

a)

Size : - min 1.6 mm & max 8 mm

b) c) d)

Type : - basic, rutile, cellulose or iron powder Condition : - concentricity, laps, chips Stroge & handling : (i) E 7016/ E 7018 = Basic = 1) Baked at 350C - 1 Hour OR as per manufacturer Recommendation. 2) Holding oven at 150C 3) Quiver at 70C - 80C (ii) E 6010/ E 6011 = Cellulose = 1) Never bake or what so ever ( Organic compound + titania ) (iii) E 6013 = Rutile = 1) may be dried at 120C - 1 hour ( titania)

9

Materials

a)

Size : - min 3.0 mm & max 25.0 mm

b)

Type : - carbon steel, alloy steel, stainless steel

c)

Condition : - some tolerance on the surface preparation

10

a) b) c) d) e) f)

Safety Fumes Electric shock Burn skin Arc rays Fire Explosion

WELDING PROCESS 11

a) b) c) 12

a) b) c) 13

Welder Contorls Arc length Angle of electrode Speed of travel Main Electrode Covering Types Rutile = general purpose > 20 ml / 100 g Basic = low hydrogen < 10 ml / 100 g Cellulose = deep penetration / fusion = up to 70 ml / 100 g Typical Of Detects Overlap, porosity, slag inclusions, excessive spatter, stray flash, incomplete penetration, excess penetration, undercut, crater cracks and lack of fusion.

14

a)

15

a)

Current ( amperage)- control the depth of penetration Amperage too low = poor penetration (tembusan) or fusion, unstable arc, irregular(tidak sama) bead shape, slag inclusions, parasity, electrode freezes to the weld, possible stray arc- strikes. Voltage Voltage too low = poor penetration, electrode freezes to work, possible stray arcs, fusion detects, slag inclusions, unstable arc, irregular bead shape.

b)

Voltage too high = Parasity, spatter, arc wander, irregular bead, slag inclusions, very fluid weld pool, positional welding difficult.

16

Speed of travel - the speed of travel affects heat input and therefore also effects metallurgical and mechanical conditions.

a)

Travel speed too fast = norrow thin bead, slag inclusion, fast cooling, (metallurgical problems), undercut, poor fusion/ penetration.

b)

Travel speed too slow = excessive deposition, cold laps, slag inclusions, irregular bead shape.

WELDING PROCESS Advantages

17

a) b) c) d) e) f) g) h) i) 18

a) b) c) d) e) f) g) h) 19

can be used in any welding position cheap welding equipment choice of consumable no need gas for shielding versatile ( can use anywhere) simple equipment simple set-up, easy to use can be used to weld thin material wide range of consumables Disadvantages low productivity wastage of consumable need proper interpass cleaning produce fumes not suitable for reactive material ( tatinium or zirconium) need oven to bake or dry the electrode not suitable for thick material high skill welder required Equipment Diagram A 1 B 1 C 1 D 1 E 1 F 1 G 1 H 1 I

= Consumables electrode = Core wire = Arc = Flux covering

A 1

D F1

B 1

E C 1

= Evolved gas shield = = = =

Slag Parent metal Weld pool Weld metal

I1 H 1

G 1

WELDING PROCESS 2b) 1 1 2 1 3 1 4 1 5 1 6 1 7 1 1

a) b) c)

Tungsten inert - gas & gas tungsten arc welding Process Characteristics Process Diagram Types of tungsten Variables Advantages & Disadvantages Types of detects Safety Process Characteristics TIG is an arc welding process usess an arc between a non- consumable electrode to the weld pool. TIG may be used with or without filler rod ( Autogeneous) Type of power source is constant current or dropping arc characteristic. u O.C.V (open circuit voltage) I :- Increase voltage, small changes in current

1 1 1 1 2 1 3 1

d) e)

- Arc blow/ wander arc blow is the deviation of the arc due to magnetic influnes. - To control arc blow if the procedure allows change to welding current from d.c to a.c 3300C to melting electrode/ filler root 1200C to melting molten pool TIG is a manual welding process but if can be mecharised. Tecnique to initiate the arc : 1) scratch start 2) high frequency start 3) pulsed start 4) lif-up start

WELDING PROCESS 2 1

Process Diagram

Power supply 1 or 3

regulator

gas silinder

Power source ( c.c ) filler rod

welding cable base metal return cable welding table

earth 3 1

a)

Types Of Tungsten THORIATED (Red colour) 1 % = High current 2 % = Low current

} steel DC -

b)

ZIRCORNIATED (Bround / grey colour) - AL - magnezium = AC

c)

CERIATED (Orange colour)

+ dageours caused cancer

- STEEL = DC d)

LATHANUM (Black colour) - STEEL = DC -

i.e : AC - AI, mg DC - Steel

X

 Grind

Grind

WELDING PROCESS 4 1

a) b) c) 5 1

Types Of Polarity DC + (Direct Current Reverse Polarity) DC - (Direct Current Straight Polarity) AC ( Altternative Current) - All mg

} steel

Affects of polarity DC +

DC -

AC

1) Electric charactertics (+)

(+)

(+)

(-)

(-)

(-) (-)

2) Heat distribution

2/3 (heat )

1/3

1/2

(-)

(+)

2/3

1/2

3) Penetration shallow

6 1 a) b) 7

1 a) b)

Types of welding machine Transformer/rectifier Inverter Types of torch Air cool torch Water cool torch

deep

moderate

WELDING PROCESS 8 1

Equipment Diagram A1 C1 B1

K1 G1

D1 E1 F1

J1 9 1

a) b) c) d) 10

A = current conductor B = shielding gas in C = welding torch D = contact tube E = non consumable tungsten electrode F = gaseous shield G = welding wire H = arc I = weld metal J = optional copper backing bar K = gas nozzle

I

H1

Types of gas Argon = Low ianisation, stable arc, easy to start the arc Helium = Hotter arc, less stable, deep penetration Argon + Helium Argon + H2 ( stainless steel Variables

a) b)

current voltage

11

Consumable

a) b) c)

size : -min 1.6mm - max 4.0 mm type : -as per parent metal condition : -store at clean and dry area or keep inside it orginal container.

12

a) b) c)

c) d)

travel speed gas flow rate

d) e) f)

electrode extension torch angle polarity

Material size : -min 1mm - max 15mm type : -can weld most materials including reactive material such as Ti and ZR condition : -must be very clean

WELDING PROCESS 13

Advantages

a) b) c) d) e) f) g)

smooth weld profile minimal cleaning required suitable for thin material can be used for out of position high quality welding process less wastage of consumables low hydrogen

14

a) b) c) d) e) f) 15

Disadvantages high skill required complex welding machine h.frequency start can interfere the electronic devices o zone (gas) not suitable for thick material low productivity Types of detects

a) b) c) d) e)

tungsten inclusion silica inclusion (ferritic steel) porosity solidification crack (autogenous TIG with fusible insert ring) root concavity

f)

crater pipe

g)

arc strike

16

a) b) c) d) e) f)

Safety arc rays fumes burn skin electric shock fire explosion

WELDING PROCESS 2c)

Gas Metal Arc Welding & Metal Inert-Gas & Metal Active- Gas

1 1 2 1 3

Process characterics Modes of transfer Process diagram Equipment diagram Advantages & disadvantages Variables Typical of detects Safety

1 4 1 5 16 1 7 81 1 1 1

a) b)

Process characterics MIG process, normally gas used : -Argon, Helium, Ar + Helium MAG process, normally gas used : -CO , CO + Argon 2

2

: -Argon + O ( stainless steel) 2

c) d)

MIG/MAG is an arc welding process used an arc between a continous filler wire to the weld pool. Type of power source is constant voltage or flat characterictics. v 2V - 2V Eregeny

100

200

I

100 A Gauges 2 1

a) b)

Modes of transfer short circuiting or diptransfer : -voltage 220 (i) (for thick materials and high deposition, non ferrous( AL,mg)) (ii) (flat and horizontal welding position) (iii) (argon or helium as a shielding gas >80 %)

WELDING PROCESS c)

globular transfer : -(i) (between dip & spray transfer current) (ii) (mechanized,co2 shielding gas,spatter level high)

d)

pulsed transfer : -(i) (utilised spray transfer during high current and low current for background current) (ii) (thin & thicker material welding, better fusion, low heat input)

2

a

} 2

3 1

}

b

more spatter caused high current & nozzle touch parameter, avoid to not touch nozzle with parameter

not torch,just high current to spray

Process diagram Power supply 1 or 3

regulator

Power source

gas silinder

Wire feeder Wire spool

Torch

welding cable base metal return cable Ground earth

welding table

WELDING PROCESS 4 1

Equipment diagram A1 A1

B1 C

B1 C1

D1 E

D

F

E1 F1

G 5 1

Type of welding machine Transformer/ rectifier Inverter

6 1

Type of welding torch Air cool (steel & thin material) Water cool (all & thick)

7 1

Type of condiut linear Steel linear - steel Teflon or nylon - AL

a) b)

a) b)

a) b) 8 1

Type of roller V Groove - steel U Groove - AI Knurled - FCAW

9 1

Variables

a) b) c)

G1

~Gas nozzle ~Contact tube ~Nozzle to work distance ~Arc length ~Electrode extension ~Contact tube to work distance ~Work piece

a)

Current

b) c) d) e) f) g)

Voltage Travel speed Electrode ectension Gas flow rate Contant tube to work distance Nozzle to work distance

10

Consumables size : -min 0.8mm - max 1.6mm Type : -as per parent metal Condition : -store at clean and dry area or keep inside it orginal container

a) b) c)

WELDING PROCESS 11

a) b) c) d) 12

a) b) c) 13

a) b) c) d) e) f) g)

Type of gas CO² (deeper penetration) Argon (for non-ferrous material{aluminium} / not suitable for steel because poor cap profile) Helium Argon + CO² (less spatter butt less penetration) Types of material Size : -min 0.8mm - max 15mm Type : -carbon, alumi, stainless steel & alloy steel Condition : -moderate cleaning Type of detects Lack of sidewall fusion (dip transfer) Solidification cracking (spray transfer) Porosity Undercut Spatter Crater pipe (star) Silica inclusions (ferritic steel)

a) b) c) d)

Safety Arc rays Fumes Burn skin Electric shock

e)

Fire

f)

Explosion

15

Advantages less wastage of consumables high productivity can weld thin and thick materials can weld most materials range of modes of metal transfer can be used for out of position (all welding position) < dip transfer spray } check can be magenacel minimum cleaning

14

a) b) c) d) e) f) g) h)

WELDING PROCESS 16

a) b) c) d) e) f) g) h) 2d) 1 1 2

1 3 4 1 5 1 6 1 7 1 8 1 9 1 1 1

a)

Disadvantages expensive welding machine need gas for shielding a lot of spatter (dip transfer) difficult to manipulate the torch high maintenance high o zone level need proper shielding when use on site not suitable for restricted access Submerged Arc Welding Process characteristics Types of flux Types of power source Types of polarity Variables Consumables Materials Types of detects Advantages & Disadvantages Process Characteristics

b)

SAW is an arc welding process uses an arc between a continous bare wire to the base metal. The arc is shielded by a fused or aglomerated flux.

c)

The arc and molten weld metal are completely submerged beneath the layer of shielding flux and are not visible to the eye, protection against the arc light is

d)

2 1

a)

therefore unnecessary. Submerged arc welding is normally fully mechanised,but may be used manually or in a fully automatic mode. Types of flux Fused : - (i) flacky appearance (ii) high resistance to moisture absorbtion (iii) good recycle (iv) smooth profile (v) good properties

WELDING PROCESS b)

3 1

a) b) c) d) e) f)

g)

Aglomerated : -(i) granular appearance (ii) very good mechanical properties (iii) need to bake prior to use- 400C - 1 hour or per manufacturer recommendation (iv) high weld quality (v) easy slag removal (vi) smooth weld profile Functions of flux to provide shielding gas to avoid atmospheric contamination to stabilise the arc to improve the properties of the weld metal by addition of alloying elements to add deoxidant to avoid surface contamination current control the depth of penetration voltage control the bead shape - (i) ↑increase voltage = more flux melting = change the properties Welding head arrangement - (i) single head with single wire -(ii) single head twin wire -(iii) tandem wire A1

C1

h)

B1 A1

B1

C1

Granular flux Electrode Copper contact block connected to power supply unit

WELDING PROCESS 4 1

Process diagram Power supply 1 or 3 Power source Flux Torch welding cable base metal return cable Ground earth

5 1

Types of power source constant voltage < 1000A constant current > 1000A

6 1

Types of polarity

a) b)

a) b) c) 7 1

DC + = (deep penetration) DC - = (higher deposition) AC = (prevent arc blow at higher current) Variables

a)

current

b)

voltage

c) d) e) f) g)

travel speed electrode extension wire size flux depth direction of travel

8 1

a) b) c) d)

welding table

Consumables Size : -min 2.0mm - max 4.0 mm Type : -as per parent metal Condition : -size,store dry and clean area or keep inside it orginal container(wire) Flux : (i) fused : -no bake required (ii) aglomerated : -baked as per manufacturer recommendation

WELDING PROCESS 9 1

Materials Size : -min 6mm - max 15.04mm Type : -carbon, stainless steel, alloy steel Condition : -moderate cleaning

10 1

Types of detects Solidification Excessive weld metal Burnthrough Porosity Lack of sidewall fusion Slag inclusions Root cancavity Undercut

11

Advantages Flux can be recycle Low weld metal cost Easily automated Low levels of o zone High productivity No visible arc light

12 1

Disadvantages Restricted welding positions Arc blow on DC current Shrinkage defects Difficult penetration control

a) b) c)

a) b) c) d) e) f) g) h) a)1 b) c) d) e) f)

a) b) c) d)

WELDING PROCESS 3)

Type of current

a)

constant current or drooping arc characteristics * when voltage increase,current will be

V

change Current large change I

v²

b)

constant voltage or constant potential or flat characteristic V

I

*

Duty cycle % = the ratio of arc time to the total time base on 10 minutes.

*

Everywelding have (O.C.V)

*

O.C.V ( AC = ~120V OR DC = ~80V )

~ = 60% Duty cycle at 350A desired current = 400A ? ~ = Duty cycle % = (rated current / desired current)² x rated duty cycle 100% = ((rated current)² / (desired current)²) x rated duty cycle (desired current) = (rated current)² x rated duty cycle = (350)² x 0.6 = 271A 4) a) b) c) d)

4 factor before welding current avoid atmospheric (shielding gas from flux covering) provide the oxidization sound weld

WELDING PROCESS 5)

Fusion welding factor( 4 factors 'essential' for fusion welding )

a) b)

fusion is achieved by melting using a high intensity heat source. the welding process must be capable of removing any oxide and contamination from the joint. atmosphere contamination must be avoided. the welded joint must process the mechanical properties required by the specification being adapted.

c) d)

6) a) b) c)

Type of polarity AC = Altternative current DC + = Direct current electrode positive/ direct current srect positive DC - = Direct current electrode negative / direct current reverse negative a

+

AC

50%

= Even 50%

+ b

70%

DC +

= (+) more -

30%

30% c

DC -

= (-) more (work piece (+)/ torch(-) for melt electrode

70%

6)



1)

GTAW = usually used DCEN (-) Reason : - a thickness of material no excess for grind and re-weld at another side of welding such b as piping.

2)

SMAW = usually used DCEP(+) Reason : most efficient for fast deposited weld metal. a

3)

FCAW & SAW = usually used DCEP(+) Reason : most efficient for fast deposited weld metal. a

WELDING IMPERFECTIONS 1 1

Imperfections any discontiniuties that the size below the "ACCEPTANCE CRITERIA" of "CODE & SPECIFICATIONS"

2 1

Defects any discontiniuties which the size above the "ACCEPTANCE CRITERIA" of any "CODE & SPECIFICATIONS". defects can be lead to : -(i) Brittle failure (ii) Fatigule failure (iii) Stress concentration area(initiation point) defects : -(i) volumetric(3 dimensional),type of defects which produce less stress raisers. (ii) planar(2 dimensional),type of defects which produce significance stress raisers.

a)

a) b)

c)

3 1

Definition This is achieved as long as the following features apply: Welds should consists of solid metal throughout a cross section at least equal to that of parent metal. (ii) All parts of a weld should be fully fused to the parent metal. (iii) Welds should have smoothly blended weld. a) (i)

4 1

a)

Weld Defects Defects which may be defected by visual inspection can be grouped under seven headings.

~ ~ ~ ~ ~ ~ ~

Root defects Contour defects Surface irregularities Cracks Lack of solid metal Lack of fusion Miscellaneous

5 1

Cracks a) Process cracks (i) Haz hydrogen cracking (ii) Weld metal hydrogen cracking (iii) Solidification cracking (iv) Lamellar tearing

WELDING IMPERFECTIONS b) (i)

Caused generally, classified by shape and position ~ classified shape = longitudinal ~ classified position = HAZ Longitudinal parent metal cracks

(ii) ~ classified shape = transverse ~ classified position = centreline(hot cracks) Transverse weld metal cracks

(iii) ~ classified shape = longitudinal ~ classified position = centreline(hot cracks) Longitudinal weld metal cracks

(iv) ~ classified shape = chevron ~ classified position = fusion zone Lamellar tearing (v) ~ classified shape = brached ~ classified shape = crater Crater cracks

WELDING IMPERFECTIONS 6 1

~ * * ~ * *

a)

Incomplete penetration other terms for the some defects are : lack of penetration lack of root penetration in the case of double sided welds terms : lack of inter-penetration lack of cross- penetration Face

(i) Incomplete filled groove

(ii) Poor cap profile

(iii) Incomplete filled groove(+) lack of sidewall fusion

b) (i)

Root Incomplete root fusion

(ii) Incomplete root penetration

(iii) Lack of interun fusion

WELDING IMPERFECTIONS 7 1

a) 1) 2) 3) 4) 5) 6) 7) b)

Causes Of Weld Defects Incomplete root penetration Causes root faces too large root gap too small arc too long wrong polarity electrode too large for joint preparation incorrect electrode angle travel speed too high for current Root Concavity ~ A shallow groove,which may occur in the root of a butt weld

1) 2) 3) 4) 5)

Causes Insufficient arc power to produce positive bead Excessive backing pressure(GTAW) Lack of welder skill Slag flooding in backing bar groove Root face too large

c)

Underfill / Incomplete filled groove

~

A weld with thickness less than that of the parent metal Causes

1) 2)

Insufficient weld metal Irregular weld bead surface

d)

Inter-run imperfections ~ Irregular along the fusion line between weld beads Causes Low arc current resulting in low fludity of weld pool Too high travel speed Inaccurate bead replacement Poor inter-run cleaning

1) 2) 3) 4)

WELDING IMPERFECTIONS e)

1) 2) 3) 4) 5) f)

1) 2) 3) 4) g)

Lack of root fusion ~ Failure of weld to extend into root of a joint Causes Excessively thick root face, insufficient root gap or failure to cut back sound metal in a "back gauging" operation Low heat input Excessive inductance in GMAW dip transfer SMAW electrode too large(low current density) Use of vertical down welding Lack of side wall fusion ~ Lack of fusion between weld metal and parent metal at one side of weld Causes Low heat input to weld Molten metal following a head of arc Oxide or scale on weld preparation Excessive inductance in GMAW dip transfer welding

1) 2) 3) 4)

Excess weld metal (reinforcement) ~ Reinforcement is the extra metal which produces convevity in fillet welds and a weld thickness than the parent metal plate in butt welds. Causes Excess arc energy (GMAW,saw) Shallow edge preparation Faulty electrode manipulation Incorrect electrode size

h)

Excess penetration ~ Projection of the root penetration bead beyond a specified limit

1) 2) 3) 4)

Causes Weld input energy to high Incorrect weld preparation i.e, excessive root gap, thin edge preparation & lack of backing Use electrode unsuited to welding position Lack of welder skill

WELDING IMPERFECTIONS i) 1) 2) 3)

Root coking / oxidized root Causes Loss or insufficient back purging gas Most commonly occurs when welding stainless steels Purging gases include argon, helium and occasionally nitrogen

Welding process : TIG Material : Stain less steel

Plate/pipe linear misalignment (HI - LO) j)

1) 2) 3) 4) 5)

Poor fit-up

Angular misalignment

Gas pores/porosity ~ Gas pores trapped within the weld metal ~ Formed by entrapped gas during the solidification of molten metal ~ Other terms which relate to entrapped gas in welds are : * Blowhole = a cavity generally over 1.5mm * Wormhole (piping) = an elongated or tubular cavity * Hollow bead = elongated porosity in the root bead (pipe line terminology) * Herving bone porosity = wormholes side by side taking on a herring bone pattern

Causes Damp fluxes/corroded elctrode Grease/hydrocarbon/water contamination of prepared surface Air entrapment in gas shield Too high arc voltage/ arc length Incorrect/ insufficient deoxidant in electrode, filler or parent metal

WELDING IMPERFECTIONS k)

1) 2) 3) 4) l)

1) 2) 3) 4) 5) m)

Surface porosity ~ Gas pores which break the surface of the weld Causes Damp or contaminated surface of electrode Low fluxing activity Excess sulphur (particularly free-cutting steels) producing sulphur oxide Loss of gas shield gas due to long arc or high breezes(GMAW) Crater pipe ~ other terms for the same defects are : * crater crack * star crack ~ A shrinkage cavity at the end of a weld run where the arc is terminated (the welder remove the welding holder were fast from parent metal) Causes Lack of welder skill due to using process with too high current Inoperative crater filler (GTAW) Too fast a coding rate Deoxidization reactions and liquid to solid volume change Contamination

1)

Arc strikes ~ Random area of fused metal where the electrode, the holder, or current return clamp accidentally touched the work and produced a short duration arc Causes Poor access to work

2)

Missing insulation on electrode holder or torch

3)

Failure to provide on insulated resting place for the electrode holder or torch when

4)

not is use Loose current return clamp

n)

1) 2) 3) 4)

Spatter ~ small droplets of electrode material can be projected clear of the weld and may fused to the parent metal Causes High arc power Magnetic arc blow Incorrect setting for GMAW process Damp electrode

WELDING IMPERFECTIONS o)

1) 2) 3) 4) p)

1) 2) 3) 4) q)

Undercut ~ An irregular groove at the toe of a run in the parent metal or in previously deposited welding, Causes Melting of top edge due too high welding current (especially at free edge) or high travel speed Attempting on HV fillet weld leg length > 9mm Excessive / incorrect weaving Incorrect electrode angle Overlap ~ An imperfection at the toe of a weld caused by metal flowing on the surface of the parent metal without fusing to it, Causes Poor electrode manipulation High energy input/ low travel speed causing surface flow of fillet weld Incorrect positioning of weld Electrode having too high a fluidity Misalignment ~ The non-alignment of two abutting edges in a butt joint

1) 2)

* Linear misalignment * Angular misalignment Causes Inaccuracies in assembly procedures or distrotion from other welds Excessive "out of flatness" in hot rolled plate or sections.

r)

Burn through

1) 2) 3) 4)

~ a localized collapse of the weld pool due to excessive penetration resulting in a hole in the root run ~ RT film = burn through = black Causes High amps/ volts Small root face Large root gap Slow travel speed

WELDING IMPERFECTIONS s)

Inclusions ~ * * * ~

1) 2) 3) 4) 5) 8 1

They are 3 types of inclusions Slag inclusions Tungsten inclusions Copper inclusions Slag or other matter trapped during welding. The imperfection is of an irregular shape and thus differs in apperance from a gas pore Causes Heavy mellscale, rust on work surface Incomplete slag removal from underlying surface of multipass weld Slag flooding a head of the arc Entrapment of slag in work surface Unfused flux due to damage coating Type of defects, suitbe record for exam ~ mechanical damage can be defined as any surface material damage cause during the manufacturing process Defects Type Porosity Cluster parosity Undercut Lack of sidewall fusion Excessive weld metal Underfill /incomplete filled groove Burn through 8) Spatter

Record  only Area (L,W) L,D L Only L,H L,D L Only

9) Overlap

L Only

1) 2) 3) 4) 5) 6) 7)

10) 11) 12) 13) 14) 15) 16) 17) 18) 19) 20)

Arc strike Mechanical damage Crack Lack of root fusion Excessive Penetration Root concavity Poor cap profile

Linear misalignment Poor stop /start Crater pipe Slag inclusions

Area (L,W) Area (L,W) Area (L,W) L Only L Only L,H L,D L Only L,H L,H  Only L,W

MECHANICAL TESTING 1 1

Mechanical testing is destructive testing of welded joints are usually carried out to : Approve welding procedures Approve welders Production quality control

2 1

Definition of mechanical testing The ultimate means by which the mechanical strength and toughness of a prepared test object can be determined by subjecting it to mechanical forces beyond the limits of its own mechanical resistance.

3 1

Properties of steel ~ mechanical properties : Hardness - a measure of the resistance to penetration Tensile strength - a metal's ability to with stand stress in tension Compresive strength - a metal's ability to with stand a pressing or squeezing together Shear strength - a metal's ability to resist a sliding past type of action Fatigue strength - ability to take repeated loading Toughness - ability to resist shock Ductility - ability of a metal's to stretches before it breaks Brittleness - metal does not stretches before it fracture

a) b) c)

a)

a) b) c) d) e) f) g) h) 4 1

a) b)

Mechanical testing is the following test have units and are termed qualitative tests Macro testing Bend

5 1

Hardness testing hardness test for measurements made by indenting the metal with a penetrator under a known load b) determined by : (i) load applied (ii) how load is applied (iii) configuration of penetration a)

c) (i) (ii) (iii) (iv)

Various methods Brinell Rockwell Vicker Knoop

MECHANICAL TESTING c(i) ~ ~ ~

BRINELL HARDNESS TESTING Hardned steel ball of given diameter is subjected for a given time to a given load Load divided by area of indentation given Brinell hardness in kg/mm² More suitable for on site hardness testing

HB =

P D 

c(ii) ~ ~ c(iii) ~ ~ ~

X ( DD² - a²

D = Size of indentor d = Depth of indentation P = Load

ROCKWELL HARDNESS TESTING Measure the hardness by the depth on indentation made by a constant load impressed upon the indentor Most common indentor is a diamond, ground to 120 degree cone with spherical VICKERS HARDNESS TESTING (micro skop) square based pyramid indenter pressed into specimen with a lead of between 1 and 100kg for 15 seconds length of diagonals measured using adjustable shutters and a built in microscope

HV = 1.825 P = 350VPN d² c(iv)

KNOOP MICROHARDNESS TESTING

~

This test is similar principal to brinell and vickers

~

Utilised low load that less than 1 kg

6 1

~ a)

Charpy Impact test objectif of test to determine the amount of energy absorbed in fracturing a standardised test place

MECHANICAL TESTING J

Ductile

T(c) -20 -10 carbon

0

10

20

Brittle change to ductile 1 1 2 1 3 1 4 1

b)

Specimens are usually taken in groups of there to allow for scatter results Test temperature should be specified Test result are give in joules Tough specimens absorb more energy than brittle specimens Charpy Impact Test (size of specimen) 45 2 mm 10

10 55

c)

root radius 0.25mm

Izod Impact Test Direction of impact TEST SPECIMEN

28 mm

Vice type fixture

d) ~ 1 1 2 1 3 1 4 1 5 1 6 1

2 mm

10 mm

Comparison of charpy test result (Bcc material) Reporting results Location and orientation of notch Testing temperature and soaking time Energy absorbed in joules Description of fracture(brittle or ductile) Lateral expansion Dimension of specimen

75 mm

30

MECHANICAL TESTING 7 1

Tensile Test a) Various methods (i) Transverse tensile (ii) All - weld metal tensile test (iii) Cruciform tensile test (iv) Short tensile test a(i) ~ ~

TRANSVERSE TENSILE TEST Objectif of test : to measure the transverse tensile strength of a butt joint under a static load. Maximum load applied = 220 KN Least cross sectional are = 2.5mm x 12mm u.t.s

= maximum load applied = u.t.s = 733.33 N/mm² Least c.s.a

1 1 2

~

Reporting results Type of specimen ( e.g - reduced section) Whether weld reinforcement is removed Dimensions of test specimen

1 5 1 6

The ultimate tensile strength in N/mm², psi or mpa Location of fracture Location and type of any flows present if any

1 3 1 4

1

a(ii) ALL - WELD METAL TENSILE ~ Object of test 1 Ultimate tensile strength 1 2 1 3 1

Yield stength Elongation % (ductility)

~

Elongation = EXTENSION X 100 ORGINAL LENGTH

~

original gauge length = 50mm increased gauge length = 64

~

Elongation % = Increase of gauge length original gauge length

X 100

(144.9 psi  1 N/mm²)

MECHANICAL TESTING ~

Elongation % = 14 X 100 50

~

Elongation = 28 %

~

Reporting results Type of specimen (e.g. reduced section) Dimensions of test specimen The u.t.s, yield

1 1 2 1 3 1 8 1

~

1 1 2 1 3

~ a 1 b c 1 d 1 e 1 4

~ a 1 b 1 c d 1 e 9 1

~ a) b) (i) (ii) (iii)

Macro/ Micro Objectif of test Macro/microscope examinations are used to give a visual evaluation of a cross- section of a welded joint. Carried out on full thickness specimens The width of the specimen should include HAZ, weld and parent place test :- macro cut the specimen grind of file polishing ( P200,P400,P600,P800,P1200) etching nital - 2% - 5% (1% - 2%) magnification x 10 ( x1000) They maybe cut from a stop/ start area on a welders approval test macro/micro (will reveal) weld soundness distribution of inclusions number of weld passes metallurgical structure of weld,fusion zone and HAZ location and depth of penetration of weld Bend Test object of test To determine the soundness of the weld zone. Bend testing can also be used to given an assessment of weld zone ductility There are three ways to perform a bend test : Face bend Root bend Side bend (generally for materials above 12mm thickness)

MECHANICAL TESTING

Compression

Tension

~ 1 1 2 1 3 1 4 1 5 1

Reporting result Thickness and dimensions of specimen Direction of bend (root,face or side) Angle of bend (90,120,180) Diameter of former (typical 47T) Appearance of joint after bending (e.g. type and location of any flaws)

~ a) b) c) d) e)

Fillet Weld Fracture Test objectif of test to break open the joint through the weld to permit examination of the facture surfaces specimens are cut to the required length a saw cut approximately 2mm in depth is applied along the fillet welds length fracture is usually made by striking the specimen with a single hammer blow visual inspection for defects

~ a) b)

Reporting results Thickness of parent material Throat thickness and leg length

c)

Location of fracture

d)

Appearance of joint after fracture

e) f)

Depth of penetration Defects present on fracture surfaces

10 1

MECHANICAL TESTING ~ a) b) c) d) e)

Nick Break Test Objectif of test to permit evaluation of any weld defects across the fracture surface of a butt weld specimens are cut transverse to the weld a saw cut approximately 2mm in depth is applied along the welds root and cap fracture is usually made by striking the specimen with a single hammer blow visual inspection for defects

~ a) b) c) d) e)

Reporting results Thickness of parent material Width of specimen Appearance of joint after fracture Depth of penetration Defects present on fracture surfaces

11 1

WELDABILITY 1 1

a) (i) (ii)

Factors which affect weldability Design access restraint

b) (i) (ii)

Metallurgical properties structure and properties of the weld metal structure and properties of the h.a.z

c) (i) (ii) (iii) (iv)

Physical properties thermal resistance coefficient of thermal expansion elastic modulus viscosity of molten material

d) Chemical properties (i) oxidation resistance (ii) surface films (iii) impurities 2 1

a) (i) (ii) (iii)

Classification of steel Plain carbon steels low carbon steel 0.01 - 0.3% medium carbon steel 0.3 - 0.6% high carbon steel 0.6 - 1.4%

b) ~

Plain carbon steels contain only : iron & carbon as main alloying elements traces of mm,si,AI,S & D may also prevent

c) ~

Alloy a mixture of two or more elements and one of the element is steel : Low alloy steels < 7% : High alloy steels > 7%

Carbon

WELDABILITY 3 1

a) b) c) d)

e) f) g) h) i) j) k) l) 4 1

a) b) c)

Steel weld metallurgy carbon : major element in steels, influences strength, toughness and ductility manganase : secondary only to carbon for strength toughness and ductility, secondary deoxidiser and also acts as a desulphuriser silicon : primary deoxidiser molybdenum : effects hardenability and has high creep strength at high temperature steel containing molybdenum are less susceptible to temper brittleness than other alloy steels chromium : widely used in stainless steels for corrosion resistance, increases hardness and strength but reduces ductility nickel : used in stainless steels, high resistance to corrosion from acids, increase strength and toughness aluminium : deoxidiser, grain refinement sulfur : machineability tungsten : high temperature strength titanium : elimination of carbide precipitation vanadium : fine grain - toughness and strength cooper : corrosion resistance and strength The grain structure of steel will influence its weldability, mechanical properties and in-service performance. The grain structure present in a material is influenced by : the type and number of elements present in the material the temperature reached during welding and or PWHT the cooling rate after welding and or PHWT 1 1

1 12 1 3 1 4 15 1

2 1 3 1

 Liquid solid metal  Corse HAZ (low toughness) Refine HAZ (improve toughness) Intercritical HAZ  Tempereded HAZ

4 1

5 1

WELDABILITY 5 1

HAZ the extent of changes will be dependent upon the following : material composition cooling rate, fast cooling higher hardness heat input, high inputs wider HAZ the HAZ can not be eliminated in a fusion weld

~

Formula calcute arc energe

~ a) b) c) d)

ARC ENERGY = V X A T.Speed

= T.Speed = mm = Heat input S

= ARC Energy X k(Thermal efficiency) mma = ~0.8 TIG = ~1.2(Autogenous) MIG/MAG = ~ 0.8 SUB-ARC = ~ 1.0 ~

Question Amps = 200 Volts = 32 Travel speed = 240mm/min Heat input

= Amps X volts Travel speed mm/sec X 1000

Heat input

= 200 X 32 X 60 240 X 1000

Heat input = 1.6 KJ/ mm

WELDABILITY 6 1

Heat Input

a) (i) (ii)

high heat input-slow cooling low toughness reduction in yield strength

b) (i) (ii) (iii)

Low heat input-fast cooling increased hardness hydrogen entrapment lack of fusion

7 1

a) b) c) d) e)

Carbon Equipvalent the C.E of steel primarily relates to its hardenability higher the C.E, lower the weldability higher the C.E, higher the susceptibilty to brittleness the C.E of given material depends on its alloying elements the C.E is calculate using the following formula ~ C.E = C +

mn 6

+

cr + mo + v 5

~ Ceq% < 0.4% = No preheat > 0.4% ~ < 0.6%  > 0.6% 

+

cu + Ni 15

Preheat ~ 150° - 200°C Low H2 consumables

Preheat ~ 300C Pwht Low H2 consumables

WELDABILITY f)

List of elements present in a steel 1 FE = Iron 21 C = Carbon 1 3 mn = manganese 14 cr = chromium 1 5 V = vanadium 6 mo = molybdenum Ni = nickel 7 8 Si = silicon 9 Ti = titanium 1 10 Nb = niobium 1 11 AI = aluminium 112 Sn = tin 1 13 S = sulphur 14 1 15 1

g)

P

= phosphorus

cu = copper

List of Gas 1 H = Hidrogen 21 HE = Helium 1 3 NE = Neon 14 Ar = Argon 1 5 Kr = Kripton 6 Xe = Xeon 7 Rn = Radon 8 F = Fluorin 9 1 10 1 11 1 12 1 13 14 1 15 1 16

CI = Klorin Br = Bromin I

= Iodin

O S Se N P

= Oksigen = Sulphur = Selenium = Nitrogen = Fosforus

17 C

= Karbon

B

= Boron

18

WELDABILITY 8 1

a) b) c)

d)

Weldability weldability can be defined as the ability of a material to be welded by most of the common welding processes,and retain the properties for which it has been designed a steel which can be welded without any real dangerous consequences is said to possess good weldability a steel which can not be welded without any dangerous consequences occuring is said to possess poor weldability. Poor weldability normally generally results in the accurrence of some sort of cracking problem Weldability is a function of many inter-related factors but these may be summarised as : 1) composition of parent material 2) joint design and size 3) process and technique 4) access

e)

There are many factors which affects weldability 1) material type 2) welding

f)

Other factors affecting weldability are welding position and welding techniques

POST WELD HEAT TREATMENT(P.W.H.T) T C 900

e)

2 1

a) b) c) 3 1

a) b) c) d)

Annealing(slos cool)

c) d)

Temperin g

a) b)

Normalisin g(AIRCOO L)

1 1

QUENCHING

723

UPPER CRITICAL TEMPERATURE

LOWER CRITICAL TEMPERATURE

C%

Structural forms of steel Ferrite : almost a pure iron and has a little carbon and is a very weak steel Cementite : actually a compound of iron and carbon known as iron carbide contain lots of carbon,as much as 1.6% - 1.8% or 2%. It strong and hard. Pearlite : solid solution,a mixture between ferrite and cementite. Austenite : It occurs at elevated temperature. It is not magnetic,as the steel heated to an elevated temperature where it becomes austenite. It structure changes from Bcc to Fcc. Martensite : Iron at room temperature that has previously been heated and suddenly quenched. Martensite is the strongest and hardnest and more a brittle structures. All heat treatment are basically cycles of there elements Heating Holding (soaking) Cooling The relevant variables for heat treatment process, which must be carefully controlled are as follows the heating rate temperature attained the time at the attained temperature(soak time) cooling rate

POST WELD HEAT TREATMENT(P.W.H.T) 4 1

a)

b) c) d) 5 1

a) b) c) d) e) f)

Objectif of P.W.H.T Post weld heat treatments are used to change the properties of the weld metal, controlling the formation of structure. Pre-heat treatments are used basically to increase weld ability,control expansion and contraction forces during welding. PWHT process in which metal in the solid state is subjected to one or more controlled heating cycles after welding PWHT is normally carried out for the purpose of stress relief, i.e : the reduction of localised residual stresses. This pwht process methods for stress relief of a welded assembly. The basic heat treatment are : Annealing Hardneng/Quenching Normalising Stress relieving Tempering Pre-heating

5(a) Annealing ~ similar with normalizing except that cooling takes place still more slowly in temperature controlled oven. 5(b) Hardnenig/Quenching ~ a controlled cooling process which causes metals to harden ~ materials must be heated at any elevated temperature, but if hardness in important, the materials should be heated above the upper critical temperature 5(c) Normalizing ~ involved heating the material above the upper critical temperature and cooling it slowly in room temperature

POST WELD HEAT TREATMENT(P.W.H.T)

1 1 2 1 3 1 4 1 5 1 6 1 7 1

Annealing & Normalizing (EFFECTS) softens weakens the materials causes ductility removes internal stresses removes distortion trends removes cracking trends Is a slow cooling process

Quenching (EFFECTS) hardens strengthens causes brittleness causes internal stresses causes distortion causes cracking Is a fast cooling process

5(d) Stress relieving (a) Stress relief (i) ~ temperature : 550 to 680 hold for sufficient time (ii)~ cooling : slow cool in air (iii)~ resulit : relieves residual stresses improves mechanical properties and increases toughness,may also be used to reduce hydrogen levels (b) Post hydrogen release (i) ~ temperature : approximately 250hold up to 10 hours (ii) ~ cooling : slow cool in air (iii) ~ result : relieves residual hydrogen 5(e) Tempering (i) ~ the process of reheating the steel after hardening or quenching to a temperature which is below the lower critical temperature followed by any rate of cooling. (ii)~ tempering is generally done between 149C - 649C and msut be done immediately after quenching. (iii)~ norminaly temperature for pwht is 500C - 650C (iv)~ effects of tempering a) b) c) d) e) f) g) h)

Hardness = Decreased Strength = Decreased Toughness = Increased Brittleness = Decreased Ductility = Increased Internal stresses = Decreased Distortion = Reduced Cracking = Reduced

POST WELD HEAT TREATMENT(P.W.H.T) 5(f) Pre-heating (1) ~ we can pre-heat metals and alloys when welding for a number of reasons. Primarily we use most pre-heat to achieve one or more of the following : (i) to control the structure of the weld metal and HAZ on cooling (ii) to improve the diffusion of gas molecules through an atomic structure (iii) to control the effects of expansion and contraction (2)~ Pre-heat controls the formation of un-desirable microstructures that are produced from rapid cooling of certain types of steels. Martensite is a desireable grain structure very hard and brittle, it is produced by rapid cooling form the austenite region. (3)~ Pre-heat temperature depends on (i) Carbon equipment ceq% < 0.4 = no preheat > 0.4 - 0.6 = 100c - 200c > 0.6 = preheat 300c (ii)

Combined Thickness t1 t1

t1

t2

t2

t4 t3

t2

t3 tc = t1 + t2

tc = t1 + t2 + t3

tc = t1 + t2 + t3 + t4

CRACK 1

a) b) c) 2

a) b) c) d) 3

a) b) c) 4

a) 5

a) b) c) d)

Process cracks hydrogen induced cold cracking (HICC) solidification cracking (HOT TEARING) weld decay When considering any type of crack mechanism, three elements must be present for it's occurrence : Stress = stresses > 0.5 of the yield stress Temperature = < 300C Hardness = > 350 VPN Hydrogen content = 15ml / 100gm of deposited weld metal Cracks characteristics causes influence controllor avoidavce Hydrogen cracking Hydrogen causes general embrittlement and in welds may lead directly to cracking Hydrogen cracking causes : 1 microstructure

~ How to control hydrogen cracking(prevention) : Preheat Control carbon equivalent High heat input Post heat 2

a) b) c)

1 HARDNESS > 350VPN(vykers pyramid number) 2 FAST COOLING 3 HIGH CARBON

Stress

Thermal contraction

1 2

Poor joint design

3

Thickness

~ Stress > 50% of yield strength of parent metal ~ How to control stress cracking(prevention) : Good fit-up Pwht Lowest strength weld metal

CRACK

3

Hydrogen

1 Hydrogen 2 Hydrocarbon 3 Hydrated oxides 4 Damp flux

a) b) c) d) 6

a) b) c) d) e) f) g) h)

~ Temperature < 200c ~ How to control Hydrogen(prevention) : Low hydrogen electrodes Low hydrogen welding process Post heat Clean surface of material Hydrogen cracking(characteristics) also known as hydrogen induced cold cracking, delay cracking, underbead cracking and chevron. hydrogen is the major influence to this type of cracking. source of hydrogen may be from maisture or hydrocarbon such as grease, paint on the parent material, damp welding fluxes or from condensation of parent material. hydrogen is absorbed by the weld pool from the arc atmosphere. during cooling,much of this hydrogen escapes from the solidified bead by the diffusion but some also diffuses into the HAZ of the parent metal. type of cracking is intergranular along grain boundaries or transganular. requires susceptible grain structure, stress and hydrogen and low temperature is reached. most likely in HAZ for carbon manganese steel and in weld meatl for HSLA steel. micro alloyed steel (hydrogen induced weld metal cracking)

7

a)

Precautions for controlling hydrogen cracking Pre-heat, removes moisture from the joint preparations, and slows down the cooling rate.

CRACK b) c) d) e) f) g) h)

Ensure joint preparations are clean and free from contamination. The use of a low hydrogen welding process such as TIG OR MIG/MAG Ensure all welding is carried out under controlled enviromental conditions. Ensure good fit-up as to reduce stress. The use of a pwht with maintaning the pre-heat temperature. Avoid poor weld profile use low hydrogen electrodes and baked as per manufacturer instructions.

8

Solidification cracking causes : metallurgical 1 a) wide freezing range → sulphur → phosporous → carbon pick up b) surface tension → can cave → depth to width ratio c) solidification phase → ferrite % → high heat input

9

Prevention for metallurgical = (a) wide freezing range control sulphur and phosphorous + add manganese control carbon clean joint preparation control dilution%

a) b) c) d) 10

Prevention for metallurgical (b) surface tension & (c) solidification phase

a) b)

convex control depth to width ratio

c)

control ferrite%

11

Solidification cracking causes 2 mechanical a) stresses → thick materials → poor joint design b) restraint → poor fit-up

12

a) b)

Prevention for mechanical (a) stresses & (b) restraint Pre heating Ensure good fit-up

CRACK 13

a) b) c)

d) e) f) g) h) i) j) k)

Solidification Cracking (characteristics) Also known as hot cracking or center line cracking or crater cracking. Solidification is observed frequently in castings and in gots can also occur in fusion welding. Solidification cracking is intergranular type of cracking that is along the grain boundaries of the weld metal. It occurs during the terminal stages of solidification, when the stresses developed across the adjacent grains exceed the strength of the almost completely solidification weld metal. Impurities such as sulphur and phosphorous and carbon pick-up from parent metal increase the risk of cracking. High joint restraint which produce high residual stress will increase the susceptibility to this type of cracking. Occurs during weld solidification process from liquidus to solidum and at the last area to solidified. Steels with high sulphur content(low ductility at elevated temperature) where by produce hot shortness to the weld metal. Fes form films at the grain boundaries whereby reduce the strength of the weld metal. Addition of manganese will form mns and forms globules instead of films.(Fes) Occur longitudinally down centre of weld. Welding process that most susceptible to this type of cracking are SAW and MIG/MAG with spray transfer due to high. A B

B

= Solid crack = Sulfur anrich liqued/filler

C

= Shrinkage stain

A

C 14

a) b) c) d) e) f) g) h)

Precaution for controlling solidification cracking use low dilution welding process the use of high manganese and low carbon content fillers maintain a low carbon content minimise the amount of stress/restraint acting on the joint during welding the use of high quality parent materials,low levels of impurities use proper joint design,use single J instead of single V clean joint preparations,free from oil,paints and any other sulphur containing product. joint design selection depth to width ratios

CRACK 15

16

a) b) c) d)

17

a) b) c) d) e) f) g)

h)

Lamellar Tearing causes : (a) poor through thickness ductility  sulfide or silicate  high sulphur (b) stress poor fit-up  poor joint  high  strength weld metal (c) hydrogen  hydrocarbon  hydrated oxides  damp flux (d) Restrain  Thick materials Prevention for lamellar tearing use Z type material control sulphur preheat, casting or forging low strength weld metal Lamellar tearing (characteristics) lamellar tearing has a step like appearance due to the solid inclusions linking up under the influences of welding stresses. occurs at beneath of HAZ or near HAZ. it forms when the welding stresses act in the short transverse direction of the material (through thickness direction) low ductile materials containing high levels of impurities are very susceptible. occurs only in rolled direction of the parent material. assiociated with restrained,joints subjected to through thickness stresses on corners,tees and fillets. presence of elongated stringers such of non-metallic inclusion such as silicates and sulfides parallel to steels rolling plane will produce poor through thickness ductility of the plate. tearing will triggered by this such non-metallic inclusions near the weld or it just outside HAZ during weld contraction.

i)

susceptible joint types :

Tee fillet weld (Lamellar Tearing)

CRACK

i)

Precautions for controlling lamellar tearing The use of high quality parent material,low levels of impurities(Z type material) Change joint design Minimise the amount of stress/restraint acting on the joint during welding The use of buttering runs with low strength weld metal Hydrogen precautions (e.g. use low hydrogen electrodes) Shift welding process such as Electro slag welding Use forging or casting joint Place soft filler wire between the joint( e.g. T joint to reduce stresses during expansion and contraction of weld metal) Pre heating helps on removal of hydrogen on the plate

~

To avoid stainless steel sensitising temperature (600c - 850c) to hall

18

a) b) c) d) e) f) g) h)

c > 0.1%

(Do not mix stainless steel material with carbon)

b) c)

Weld Decay (characteristic) Weld decay may occurs in unstabilized austenitic stainless steel with carbon content above 0.1%. Also known as knife line attack or crack. Chromium carbide precipitation takes place at the critical range of 600-850C

d)

At this temperature range carbon is absorbed by the chromium,which causes a local

e)

reduction in chromium content by promoting chromium carbides. Loss of chromium content result in lowering the materials resistance to corrosion attack allowing rusting to occur.

19

a)

(sensiting temperature).

CRACK 20

a) b) c)

21

a) b) c) d) e) 22

a) b) c) d) e) f)

23

a) b) c) d) e) ,

Precautions for weld decay The use of a low carbon grade stainless steel (e.g. 304L,316,316L with carbon content < 0.03%). The use of a stabilized grade stainless steel( e.g. 321,347,348 recommended for severse corrosive conditions and high temperature operating conditions). Standard grades may require PWHT, this involves heating the material to a temperature over 1100°C and quench the material,this restores the chromium content at the grain boundary, a major disadvantage of this heat treatment is the high amount of distrotion. Fatigue Failure(INITIATION POINT + PROPAGATION) - to avoid fatigue failure : grinding with burn grinder P.W.H.T Painting & coating Plening Weld the toe with t.i.g or plasma T.I.G Fatigue Failure(Characteristics) Fatigue cracks occur under cycle stress conditions Fracture normally occurs at a change in section,notch and weld defects(i.e. stress concentration arc) All welded materials are susceptible to fatigue cracking. Fatigue cracking start at a specific point referred to as a initiation point. The fracture surface is smooth in appearance sometimes displaying beach markings. The final mode of failure may be brittle or ductile or a combination of both. Precautions against fatigue cracks Toe grinding,profile grinding The elimination of poor profiles. The elimination of partial penetration welds and weld defects. Operating conditions under the material endurance limits. The elimination of notch effects(e.g. mechanical damage cap/ root undercut)

SYMBOLS 1 2 3 1

a)

BS 499 PART 2 BS EN 22533/ISO 2553 AWS 2.4 BS 499 PART 2 Arrow profile Reference Line Tail Arrow Line

Other side information

Arrow side information

b)

Butt Weld profile









SYMBOLS c)

Fillet weld profile















SYMBOLS d)

Fillet Weld Dimension

b10 10

 10

s = 15 s15



a=7 a7

a = Norminal design throat b = Leg length c = Depth of penetration e)

Intermitent Fillet Weld n = number of weld Length of weld e = Distance between weld element

n X (e)

50

50

100 100 100

v3 x 100(50)

SYMBOLS f)

Stagered intermittent fillet weld

nx

(e)

other side g)

Type of Arrow

NDT

WPS



Field weld(site weld)



Welding to be carried out all round component (peripheral weld)



The component requires NDT Inspection



Addition information,the reference document is included in the box



Partial penetration single - V-butt



Plug weld



Spot weld



Seam weld



Square butt weld



Single - V butt broad root face



Edge flange weld

10 10

SYMBOLS h)

Flared flange welding symbols

Joint detail 

2

a)

BS EN 22533 / ISO 2553 Arrow profile

Identification Line(other side information)  reference line(arrow side information)

b)

Butt weld profile

m

 mR

s10 10

Single - V butt with permanent backing strip

SYMBOLS c)

Fillet weld profile







d)

e)

Type of arrow 

Plug weld



Spot weld



Seam weld



Square Butt weld



Steep flanked single- V butt



Surfacing

Arrow profile Z6 6mm leg

NOTE : fillet weld Z = leg length(EN) / fillet weld b = leg length(BS)

RESIDUAL STRESS 1

Level of residual stress ~ yield strength of parametal at room temperature.

2

Level of residual stress after P.W.H.T. ~ yield strength of parent metal during P.W.H.T Disdebion of stress

3

A

A'

B

B'

C

C'

B'=

D'

C'=

D

A'=

D'= 4

Normal stress ~ stress arising from a force perpendicular to the cross

5

Shear stress ~ stress arising from forces which are parallel to and lief in the plane of the cross sectional are.

Shear stress

example : most critical (100 % NDT)

RESIDUAL STRESS 6

a)

b) c) d) e) f) g) h) i) j) 7

a) b) c)

Hoop stress Stress acting circumferentially around a pipe due to internal pressure

Metal contract during solidification and subsequent cooling. If this contraction is prevented or in hibited. Residual stress will develop. The tendency to develop residual stresses increases when the heating and cooling is localised. Welding is very localised heating and the presence of liquid and solid metal in contact can be expected to induce very high levels of residual stresses. Residual stresses are very difficult to measure with any real accuracy. Residual stresses are self balancing internal forces and not stresses induced whilst applying external load. Stresses are more concentrated at the surface of the component. The removal of residual stresses is termed stress relieving. Residual stresses occur in weld in the following directions. along the weld  longitudinal residual stresses. across the weld  transverse residual stresses. through the weld  short transverse residual stresses. compression Longitudinal

Tension

Short transverse Transverse

RESIDUAL STRESS 8

a) b) c) d) ~ ~ ~ ~ ~

Factors which affect distortion material properties and condition heat input the amount of restain the amount of weld metal deposited Distration will occur in all welded joints if the material are free to move( i.e not restrained). Restrained materials result in low distration but high residual stress. More than one type of distration may occur at one time. Highly restrained joints also have a higher crack tendency to joints of a low restraint. The action of residual in welded joints is to causes distrotion. TYPE OF DISTORTION Longitudinal Distortion

DIRECTION OF DISTORTION

Bowing Distortion Transverse Distortion Angular Distortion

a) b)

Control of distration my be achived in on of the following way The used of a different joint design Offsetting the joints to be welded- so that the metal distorts in the required position.

c)

The use of a balanced welding technique.

d)

The use of clamps,jigs and fixtures.

e)

Use low heat input electrode.

f) g)

Control the heat input. Pwht after weld.

9

WELDING CONSUMABLES 1

a) b) c) d) e)

Objectif Consumables used in arc welding may be a combination of wire and flux, or bare solid wire. Flux may be present either as a core-for some m.a.g applications. Flux coating present for SAW process. M.I.G and T.I.G process which use bare solid wire and no flux. Consumables which are added separately to the weld pool may be know as filler rods or filler wires,if they are part of the welding circuit providing one end of the arc,they are know as electrodes.

Electrode code(samples) BS EN 440 1994( G 463 M G3 Si 1) G = wire electrode and/or deposit/ gas shielded metal arc welding. 46 = strength and elongation in the all weld metal condition(i.e 460 minimum yield strength N/mm², 530-680 tensile strength N/mm², 20% minimum elongation). 3 = impact properties,temperature for minimum average impact energy of 47J. m = shielding gas as to BS EN 439. The symbol "m" for mixed gasses,the symbol "c" for shielding gasses. G3 Si 1 = chemical composition of the wire electrode(i.e silicon,manganese,aluminium etc. contents.) 2

a)

b)

Aws (E 7018m) E = electrode 70 = 70,000 psi specified minimum ultimate tensile strength. 1 = welding position suitable (all position) 8 = flux type and electrical characteristic m = resistant to moisture pick up

c)

Aws (E 7018G) E = Electrode 70 = 70,000 psi specified minimum ultimate tensile strength 1 = Welding position suitable(all position) 8 = Flux type and electrical characteristic G = Low alloy steel (alloy content)

WELDING CONSUMABLES d)

BS E 51 33B 160 2 0(H) E = Electrode 51 = Strength 33 = Toughness B = Covering 160 = Efficiency(%) 2 = Positional capability 0 = Electrical capability (H) = Low hydrogen potential

3) Electrode content (i)a) MMA/SMAW  (i) Basic

1 2 3

Note : Polarity DC + OR AC (ii) Rutile

1 2 3

E7016 = Potasium E7018 = Iron powder,calcium carbonate E9015 = Sadium

E6013 = Titania oxide,potasium E6012 = Sodium E6014 =

Note : Polarity DC + OR DC- OR AC (iii) Cellulose

1 2

Note : Polarity DC + (iv) Iron powder b)

E6010 = Sodium,organic compound E6011 = Potasium,organic compound

E7024 = Flat welding position

MIG/MAG = Filler wire gasses = ER 70 S-G ER = Rod or electrodes 70 = Strength s = Solid g = Electrical charasteristic,manufacturer impormation,alloys

c) d) e)

TIG = Filler rod gases SUB ARC & SAW = Filler wire flux OFW = Filler wire gases flux

WELDING CONSUMABLES (ii)a) Each consumables is critical in respect to (i) Size (ii) Classification/supplier (iii) Condition (iv) Handling and storage (v) Treatments (e.g baking/drying) (iii)a) Welding consumables for mmA/SMAW (1) Consist of a core wire typically between 350 - 450mm in length and from 2.5-6mm in diameter. (2) The wire is covered with an extruded flux coating. (3) The core wire is generally of a low quality rimming steel. (4) The weld quality is refined by the addition of refining agents in the flux coating. (5) The flux coating many elements and components that all have a variety of functions during welding. Sample : E 51 33B compulsory

b)

160 20H optional

2

Rutile electrodes : used mainly on general purpose work low pressure pipe work,support brackets

c)

Flux constituents include :

1

Titanium dioxide,slag former and arc stabilizer

2

Cellulose - slag and improve viscosity

1

3

Potasium silicate - ioniser and binder

d)

Advantages for rutile electrodes Easy to use Low cost/control Smooth weld profiles Slag easily defachable High deposition possible with the addition of iron powder

1 2 3 4 5

WELDING CONSUMABLES e) 1 2 3 4

f) 1 2 3 4

g) 1 2 3

h) 1 2 3 4 5

i)

Disadvantages for rutile electrodes High in hydrogen High crack tendency Low strength Low toughness values Cellulose electrodes : Used mainly for pipeline welding Suitable for welding in all position especially vertical down,stove technique They produce a gas shield high in hydrogen Deep penetration/fusion characteristic Flux constituents include : Cellulose,natural organic compounds Titanium dioxide - slag former Sodium silicate - main ionizers Advantages for cellulose electrodes Deep penetration/fusion Suitable for welding in all positions Fast travel speeds Large volumes of shielding gas Low control

1

Disadvantages for cellulose electrodes High in hydrogen

2

High crack tendency

3

Rough cap appearance

4

High spatter contents

5

j) 1 2 3

Low deposition Basic electrodes : Used mainly for high pressure work and for materials of high tensile strength. They are capable of producing welds of a low hydrogen content. Prior to use they may be baked to give a low hydrogen potential typically 300C for 1 hour plus.

WELDING CONSUMABLES k)

Flux constituents include : Limestone (calcium carbonate) - gas former Fluorspar - improve fluidity of slag Sodium silicate/potassium silicate - main ionizers

1 2 3

l)

Advantages for basic electrode High toughness values Low hydrogen contents Low crack tendency

1 2 3

m) 1 2 3 4 5

Disadvantages for basic electrodes High cost High control High welder skill required Convex weld profile Poor stop/start properties

(iv)a) TIG welding consumables (i) Consists of a wire and gas,though tungsten electrodes being classed as non-consumables may be considered consumables (dia 1.6 - 10mm). b) MIG/MAG welding consumables (i) Consists of a wire and gas the same quality as for TIG wire. c) Solid wire Aws 5.18 (ER XXS - X) ER = Designates an electrodes or rod XX = Indicates minimum tensile strength (with co2) S

= Indicates a bare solid electrode or rod

X

= Specifies chemistry,impact properties and hence applications

(v)

Electrodes's baked at temperature and holding time.

a)

Electrode : 7016 & 7018 : Baked at 350C  1 Hour OR as per manufacturer recommendation. : Holding oven at 150C : Quiver 70C → 80C

WELDING CONSUMABLES b)

Electrode : E6013 : Dried max 120C

c)

Electrode : E6010 : Never baked or dried : Batch certificate

WELDER PROCEDURES AND WELDER TEST 1)

WELDING PROCEDURE

(i)a) ~ ~ ~ ~ ~

A welding procedure showns all the variable involved with the production welding Welding process Technique Consumable type Material Preheat

b)

Once the content of a written procedure has been approved, a weld is made in accordance with the requirements of that procedure,this is known as a welding procedure test or welding procedure qualification test (PQR).

c)

The welding procedure made,this will depend on whetever the proposed change is an essential or non-essential variable.

d)

Do all welding procedures need to be written most production welding procedure are formatted on written documents or computer spread sheet,but they need not be written and may be a product of experience.

e)

Other variable specific to the welding process (i.e : flux type for submerged arc welding shielding gas and gas flow rate for gas shielded processes.)

f)

Inspection of welding procedure test welds,when a procedure weld has reached ambient temperature or when otherwise specified it undergoes examination by NDT and destructive testing. Welding inspector to mark up the areas on the weld which require the removal at test coupons for mechanical testing. These test areas are normally specified in the applicable specification.

(ii)

Approval of welding procedure

a)

Once the weld has been completed it is usually visually inspected,then radiography or ultrasonic testing is usually applied.

b)

Finally, and most important mechanical test are performed to ensure that the desired level of mechanical properties have been meet.

WELDER PROCEDURES AND WELDER TEST c)

If a desired properties have been meet,then a procedure qualification record (PQR or WPAR) is completed with all the test results,and the procedure than becomes qualified.

d)

From this data, a workable document for production welding is prepared and called a welding procedure specification(WPS).

e)

A cswip 3.2 senior welding inspector is normally responsibles for the testing welding procedure specification.

(iii) Welding procedure approval terms * Definitions a)

Essential variables : variable which influence the mechanical and metallurgical properties.

b)

Range of approvals : the extent of approvals for an essential variable.

c)

Examining body : organisation who verifies compliance.

(iv)

Welding procedure approval term (example of extent of approval include :)

a) b) c) d)

Diameter of pipe or thickness of plate. Welding position,amperage range or number of runs. Welding process( on multi process procedures only) Change of consumable to one of the same classification

e)

Heat input range

(v)

Welding procedure approval(code BS) BS EN 288 Part 3

(vi) a) b) c) d) e) f) g)

Welding procedure (producing a welding procedure involves :) Planing the tasks Collecting the data Writing a procedure for use of for trial Making a test welds Evaluating the results Approving the procedure Preparing the documentation

WELDER PROCEDURES AND WELDER TEST (vii) Welding variables list showns the variables which are likely to encountered on welding procedure: a) Welding process b) Joint design c) Welding position d) Joint cleaning,jigging and tack welding e) Welding technique f) Back gounging g) Backing h) Filler metal classification,manufacture,trade name and dimension i) Filler metal and flux drying procedure j) Electrical parameters(type current,amperage,voltage,polirity(d.c)) k) Travel speed and wire feed speed(mechanized welding) l) Preheat temperature m) Interpass temperature n) Past weld heat treatment o) Material (viii) Approving the procedure a) When the data has been collected,the procedure must be validated by producing a test weld,weld procedure test(WPT). b) A number of standards provides information. (xi) Object of a welding procedure test a) To give maximum confidence that the welds mechanical and metallurgical properties meet the requirements of the applicable code/specification. b)

Each welding procedure will show a range to which the procedure is approved (extent of approval)

(xii) Welding procedure specification a) A document providing in detail the required variables for a specific application to ensure repeatability. (xiii) Procedure qualification record a) A record comprising all relevant data from the welding of a test piece needed for approval of a welding procedure specifications as well as all results from the testing of the weld test.

WELDER PROCEDURES AND WELDER TEST (x) Welding variables a) Essential variables ~ Essential variables are those in which a change,as described in the specific variables,Is considered to affect the mechanical properties of the weldment,and shall require requalification of the WPS (e.g. base metal thickness,P no. or F no and etc). b) ~

Non essential variables Non essential variables are those in which a change, as described in the specific variables, may be made in the WPS without requalification. (e.g. change groove design,etc)

c)

Supplimentary essential variables ~

Variables are required for metals for which other section specify notch- toughness test are in addition to the essential variables for each welding process. (e.g. change group no,base metal thickness limit,pwht, preheat temperature and etc)

(xv) ASME a) Shall ~ a mondatory practise which will require change of WPS if not followed. b)

Should ~ a recommended practise.

2) (i) a)

WELDER TEST Objectif A welder test,also known as a welder qualification test (W.Q.T), or welder approval test is carried out to ensure the welder is a able to produce a sound weld that meets the requirements of the relevant welding procedure and application specification.

b)

If a change was proposed outside a specified limitation, a new welder qualification test would have to be made,because this would be a change of an essential variable.

c)

To give maximum confidence that the welder meets the requirement of the approved procedure(WPS)

d)

The test weld should be carried out on the some material and some conditions as for this site welds.

e)

The welder who carries out the procedure qualification weld automatically qualify when the procedure qualifies.

WELDER PROCEDURES AND WELDER TEST f) 1) 2) 3) 4) 5) 6) 7)

Welding variables Parent material type Consumable or shielding gas type Dimensions of parent material Welding position Types of joint Preheat temperature Post weld heat treatment procedure

(ii) a) b)

Welder qualification test To determine the welder's ability to deposit sound weld metal. The purpose of the qualification test for the welding operator is to determine the welding operator's mechanical ability to operate the welding equipment.

(iii) Welder approvals a) Once the procedure has been approved it is then important to test each welder, to ensure that he has the skill to reach the minimum level of quality in the weld,as laid down in the application standard. b) There is no need to carry out the mechanical test of the procedure,although bend tests are often weld to ensure good sidewall fusion. c) Normally,visual,x-ray,bends,fracture and macro are used in welder approval tests. (iv) a)

Welder approval standards EN 287 : Part 1 - steel Part 2 - aluminium and its alloys

b)(i) Defines

Welder approval

(iv)

Testing requirements

(ii) Essential variables

(v)

Acceptance requirements

(iii) Range of approvals

(vi)

Re test

(vii) Period of validity (v) a) b) c)

Information that should be included on a welders test certificate are : Welders name and identification number Date etc

WELDER PROCEDURES AND WELDER TEST NOTE : 1 2 3

A welding procedure test proves the weld/welding A welder qualification test proves the welders ability to weld in accordance with procedure. Preliminary WPS PQR Qualification

Record

result ok

Final WPS

transfed

NON-DESTRUCTIVE TESTING 1 2 3 4 5

Penetrant Testing Magnetic Particle Testing Eddy Current Testing Ultrasonic Testing Radiographic Testing

NOTE :

1 2

1

(i) a) (i) (ii) (iii) b) c) d) e) f) g)

Penetrant & magnetic Ultrasonic & radiography

surface defects internal defects

Penetrant Testing Objectif also known as a Dye Penetrant inspection(DPI) Penetrant flaw detection(PFD) Liquid penetrant inspection(LPI) this surface inspection con't applicable to all non-parous,non-absoring material. penetrating fluid(penetrant) applied on to component and drawn into defect by capillary action. this type of testing uses the forces of capillary action to defect surface breaking defects. it is impossible to defects which do not break the surface with this method. but it can be used on both magnetic and non-magnetic materials providing they are non-porous. there are several types of penetrant system,this included the following which are shown in a descending order of flaw detection sensitivity.

(i) Post emulsifiable (ii) Solvent based (iii) Water based

fluorescent "normally use at dark place "

(iv) Solvent based (v) Water based

colour contrast

h)

Fluorescent penetrant require the use of an ultraviolet(UV-A) light to view indications, whilst colour contrast penetra are viewed with the naked eye.

i)

One of the most common site used penetrant systems use solvent based colour contrast penetrants in aerosls. A typical sequence of operations on a steel test item is as follows.

NON-DESTRUCTIVE TESTING (ii)

How to apply

a)

clean are using wire brush,cloth and solvent. On aluminium,other soft alloys and plastic,wire brushing should not be used,as there is a danger that surface breaking defects may be closed.

b)

apply penetrant- leave for 15 minutes.colour contrast penetrants are normally red in colour and should remain on the part long enough to be drawn into any surface discontinuities. This time can vory from about ten minutes to several hours depending on the type of material and size/type of defects sought.

c)

remove surface penetrant using cloth and solvent. Apply solvent to the cloth and not directly on to the work piece. Clean thoroughly.

d)

apply developer- leave for 15 minutes. The developer draws any penetrant remaining in any surface breaking discontinuities with a blotting action.

e)

interpet area. Any discontinuities are indicated by a red mark, (e.g. line or dot againts a white background. Fluorescent penetrants would show green-yellow when viewed with an ultraviolet(UV-A) light.

(iii)

Advantages

a) b) c)

very sensitive can be uses on non-ferrous metals,some plastics and class small objects with complex geometry can be inspected

d)

no power supply needed

e)

great skill not require

f)

can be applied in batches (Low operator skill)

(iv) a) b) c) d) e) f) g)

Disadvantages can only detect defects open to the surface surface penetration is critical the method is time consuming messy process interpretation sometimes difficult do not applied to pointed objects effluent problem with waste

NON-DESTRUCTIVE TESTING 2

(i)

Magnetic Particle Testing Objectif

a)

This method of NDT may defect surface and in certain cases,slight sub-surface discontinuities up to 2-3 mm below the surface.

b)

Test method for the detection of surface and sub-surface indications in ferromagnetic materials.

c)

Defects revealed by applying ferromagnetic particles.

d)

Magnetic field induced in component.

e)

Defects disrupt the magnetic flux.

f)

This process can scan 10mm of parent metal.

g)

A magnetic field is introduced into a specimen to be tested,fine particles of ferromagnetic powder, or ferromagnetic particles in a liquid suspension, are then applied to the test area. Any discontinuity which interupts the magnetic lines of force will create a leakage field,which has a north and south pole on either side of it. This attracks the ferromagnetic particles in great numbers.The discontinuity may show as black indication against the contrasting background usually a dark violet background.

h)

When m.p.i. is carried out using fluoresent inks the use of an ultraviolet(UV-A) light is necessary to cause fluorescence of the particles,although there is no need to aplly a contrast paint.

i)

Fluorescent ink methods are more sensitive than black ink methods.

(ii) a) b) c) d) e) f)

Advantages Will detect some sub-surface defects Rapid and simple to unders Pre-cleaning not as critical as with DPI Will work through thin coatings Cheap rugged equipment Direct test method (simple tv use, little surface preparation requires)

NON-DESTRUCTIVE TESTING (iii) a) b) c) d) e) f) 3

Disadvantages Ferromagnetic materials only Requirement to test in 2 directions Demagnetisation may be required Odd shaped parts difficults to test Not suited to batch testing Can damage the component undertest Ultrasonic testing Probe CRT Screen

couplant CRT

A-C (Current)

material

crystal ultrasonic (>20,000 herts)

First signal

50 mm

back signal 100 mm

(i)

Advantages

a)

It is good for planar defect (e.g. crack,lack of fusion,lack of root penetration) (may be battery powered)

b)

Deep of defects (Both surface & sub-surface detection) (Safe) (Capable of measuring the depth defects) (Portable)

NON-DESTRUCTIVE TESTING 4

(i) a) b)

Radiographic Testing Types of Radiographic testing X-ray Gamma ray

1) X or gamma radition is imposed upon a test object. 2) Radiation is transmitted to varying degrees depent.

with asses Dence inclusions

Low dence -inclusion,porosity,slag -darker

Film

(ii)

Density - relates to the degree of darkness contrast-relates

Film interpet

(0.40)

Sensivity = Thickness wire visiable X 100 Parent metal (16) Darker

= 2.5 % Lighter

Inoder 2% 2 x 16 100

UT( disadvantages) Trained & skilled operator required Requires high operator skill Good surface finish required Defect identification Couplant may contaminate No permanent record

= 0.32

NON-DESTRUCTIVE TESTING Advantages RT 1) 2) 3) 4) 5) 6)

Permanent record Little surface preparation Defect identificates No material type limitation No so reliant upon operator skill Thin material

Disadvantages 1) 2) 3) 4) 5) 6) 7) 8)

Expensive consumables Bulky equipment(X-ray) Harmful radiation Can't defect lamination Defect require significant depth in relation to the radiation beam Slow result Very little indication of depth Access to both side required

ETC 1

a)

AWS ~ American Welding Society

b)

ASNI ~ American National Standards Institute

c)

ASME ~ The American Society Of Mechanical Engineers

d)

ASNT ~ American Society Of Non destructive Testing

e)

ASTM ~ American Society For Testing and Material

f)

WPS ~ Welding Procedure Specification

g)

PQR ~ Procedure Qualification Record

h)

PJP ~ Partial Joint Penetration

i)

CPJ ~ Completed Joint Penetration

j)

WOQ ~ Welding Operator Qualification

k)

WQT ~ Welder Qualified Test

l)

WQR ~ Welding Qualified Test

m)

WPQR ~ Welding Performance Qualification Record

ETC n)

AFC ~ Approved For Construction

o)

PWHT ~ Post Weld Heat Treatment

p)

CR ~ Calibration Records

q)

ITP ~ Inspection Test Plan

r)

MIR ~ Material Inspection Record

s)

WTR ~ Weld Traceability Record

t)

MRN ~ Material Received Note

u)

NDT ~ Non Destructive Testing

v)

DT ~ Destructive Testing

w)

RT ~ Radiographic Testing

x)

UT ~ Ultrasonic Testing

y)

DPT ~ Dye Penetrant Testing

z)

RIS ~ Radiation Imaging System

ETC A)

MPI ~ Magnetic Particle Inspection

B)

API ~ American Petrolium Institute

C)

JIS ~ Japan Industrial Standards

D)

BS ~ British Standards

E)

CSWIP ~ Certification Scheme For Welding and Inspection Personnel

F)

PCN ~ Personnel Certifiation in Non-Destructive Testing

2

(A) Section stamp (i)

u¹ ~ Vessel (ASME & Dev 1)

(ii)

u² ~ Vessel (ASME & Dev 2)

(iii)

S ~ Boiler (ASME 1)

(iv)

P ~ Piping (ASNI B31.1)

(v)

R ~ Repair work boiler

ETC (B)

ASME CODE

(i)

ASME 1(I) ~ Boiler/ fired vessel fabrication

(ii)

ASME 2(II) PART A ~ Material ferrous(kandungan besi)

(iii)

ASME 2(II) PART B ~ Material non-ferrous (kandungan tanpa besi)

(iv)

ASME 2(III) PART C ~ Consumeables/electrodes

(v)

ASME 5(V) ~ Non-Destructive Testing

(vi)

ASME 8(III) Dev 1 ~ Pressure vessel

(vii)

ASME 8(VIII) Dev 2 ~ Pressure vessel(special design)

(viii)

ASME 9 (IX) ~ WPS & Welder performance

(ix)

ASNI B 31.1 ~ Power Piping(boiler)

(x)

ASNI B 31.3 ~ Chemical plant

ETC 3

a) b) c) d)

CALIBRATION CALCUTION 3 reading (x),(y),(z) (A) = Actual (P) = Preset (D) = Deviation x+y+z 3 A-P P

= A

X 100 =

maximum  10%  1% minimum if (-) rejected

 10 1

preset - 100 actual reading(average) - 92 % maximum  +10% & % minimum  -1%

1)

Position of welding for plate only

a) ~ Down hand & position 1G/F b) ~ Horizontal & position 2G/H c) ~ Vertical & position 3G/V d) ~ Overhead & position

100 -(-) 92 (-) 8 ACCEPT

ETC 2)

Plate preparation for WQT 4"

4"

8"

4 " = 101.6mm 8 " = 203.2mm

3)

How to select pressure gauge ?

~

Test required is 500 p.s.i



required test 500 p.s.i x not less than 1.5 = 750 p.s.i (we can select pressure gauge not less than 750 p.s.i)



preferably 500 p.s.i x 2 = 1000 p.s.i (select pressure gauge more than 1000 p.s.i)

~

According to ASME I - PW 5A Hydrostatic Test.